A variety of products such as surfactants, functional fluids, glycol ethers, polyols, and the like, are commercially prepared by the condensation reaction of alkylene oxides with organic compounds having at least one active hydrogen, generally, in the presence of an alkaline or acidic catalyst. The types and properties of the alkoxylation products depend on, among other things, the active hydrogen compound, the alkylene oxide, and the mole ratio of alkylene oxide to organic compound employed, as well as the catalyst. As a result of the alkoxylation, a mixture of condensation product species are obtained having a range of molecular weights.
In many applications of alkoxylated products, certain of the alkoxylation species provide much greater activity than others. Consequently, alkoxylation processes are desired that are selective to the production of those alkoxylation species. Further, for many of these uses, mixtures of alkoxylation products falling within a narrow range of molecular distribution of reacted alkylene oxide are believed to be superior to alkoxylation products in which a single alkoxylation specie predominates. For example, in a surfactant composition the range of materials on which the surfactant will be required to operate will normally vary. A range of alkoxylation species, even though narrow, will enhance the performance of the surfactant to the variety of materials which it may encounter. Further, mixtures of closely related alkoxylation species can provide a mixture having other improved properties such as in respect to cloud point, freezing point, pour point and viscosity as compared to a single specie. There, however, is a balance, and if the distribution of species becomes too broad, not only are less desirable alkoxylation species diluting the mixture, but also the more hydrophilic or lipophilic components than those in the sought range can be detrimental to the sought properties.
Moreover, a wide range of alkoxylation species can restrict the flexibility in ultimate product formulation using the alkoxylation reaction product. For example, in making oil in-water emulsion products it is often desired to prepare a concentrated composition that minimizes the weight percent of water. This concentrate may then be diluted with water at the time of use, thereby saving the expense of shipping and storing water. The ability to form a desirable concentrate is generally dependent, in part, on having a narrow distribution of alkoxylation species since if heavier moieties are present, a greater portion of water is usually required otherwise gelling (evidencing product instability) may occur.
The recognition that certain distributions of moles of alkylene oxide to moles of organic compound in alkoxylation products can be important has long been recognized. For example, British Patent Specification No. 1,399,966 discloses the use of ethoxylates having a hydrophilic lipophilic balance (HLB) of from about 10 to about 13.5 for use in a laundry detergent. In order to provide this HLB, the moles of ethylene oxide reacted per mole of fatty alcohol is described as being critical. In British Patent Specification No. 1,462,133, the sought cleaning composition employed alkylene oxide cosurfactants sufficient to provide even a narrower HLB, i.e., from about 10 to about 12.5. In British Specification No. 1,462,134, a detergent composition is disclosed which uses ethoxylates having an HLB of from about 9.5 to 11.5, with the preferred ethoxylates having an HLB of 10.0 to 11.1.
Thus, with the increased understanding of the properties to be provided by an alkoxylation product, greater demands are placed on tailoring the manufacture of the alkoxylation product to enhance the sought properties. Accordingly, efforts have been expended to provide alkoxylated products in which the distribution of reacted alkylene oxide units per mole of organic compound is limited to a range in which the sought properties are enhanced.
Alkoxylation processes are characterized by the condensation reaction in the presence of a catalyst of at least one alkylene oxide with at least one organic compound containing at least one active hydrogen. Perhaps the most common catalyst is potassium hydroxide. The products made using potassium hydroxide, however, generally exhibit a broad distribution of alkoxylate species. See, for example, M. J. Schick, Nonionic Surfactants, Volume 1, Marcel Dekker, Inc., New York, NY (1967) pp. 28 to 41. That is, little selectivity to particular alkoxylate species is exhibited, especially at higher alkoxylation ratios. For example, FIG. 6 of U.S. Pat. No. 4,223,164 depicts the distribution of alkoxylate species prepared by ethoxylating a fatty alcohol mixture with 60 weight percent ethylene oxide using a potassium catalyst.
The distribution that will be obtained in alkoxylation processes can vary even using the same type of catalyst depending upon the type of organic compound being alkoxylated. For example, with nonylphenol, a Poisson-type distribution can be obtained using a potassium hydroxide catalyst. However, with aliphatic alcohols such as decanol, dodecanol, and the like, the distribution is even broader. These distributions are referred to herein as "Conventional Broad Distributions".
Acidic catalysts can also be used, and they tend to produce a narrower, and thus more desirable, molecular weight distributions; however, they also contribute to the formation of undesired by-products and, thus, are not in wide use commercially.
Particular emphasis has been placed on controlling molecular weight distribution of alkoxylation products. One approach has been to strip undesirable alkoxylate species from the product mixture. For instance, U.S. Pat. No. 3,682,849 discloses processes for the vapor phase removal of unreacted alcohol and lower boiling ethoxylate components. The compositions are said to contain less than about 1% of each of non ethoxylated alcohols and monoethoxylates, less than 2% by weight of diethoxylates and less than 3% by weight of triethoxylates. This process results in a loss of raw materials since the lower ethoxylates are removed from the composition. Also, the stripped product still has a wide distribution cf ethoxylate species, i.e., the higher molecular weight products are still present in the composition to a significant extent. To circumvent viscosity problems which would normally exist with straight-chain alcohols, about 20 to 30 percent of the starting alcohol is to be branched according to the patent.
Obtaining a narrower distribution of alkoxylated species at lower epoxide reactant to organic compound mole ratios can be readily accomplished. U.S. Pat. No. 4,098,818 discloses a process in which the mole ratio of catalyst (e.g., alkali metal and alkali metal hydride) to fatty alcohol is about 1:1. Ethoxylate distributions are disclosed for Parts C and D of Example 1 and are summarized as follows:
______________________________________ Part C Part D ______________________________________ Primary fatty alcohol 12 carbons 12 to 14 carbons Moles of ethylene oxide 3.5 3 per mole of alcohol Product molecular 352 311 weight Average ethoxylation 3.8 2.54 Distribution, % E.sub.0 0.7 3.8 E.sub.1 6.3 15.3 E.sub.2 17.3 25.9 E.sub.3 22.4 23.8 E.sub.4 21.2 15.9 E.sub.5 15.6 10.7 E.sub.6 8.6 3.5 E.sub.7 5.6 1.2 E.sub.8 2.3 -- ______________________________________
The high catalyst content in combination with the low alkylene oxide to alcohol ratio appears to enable a narrow, low ethoxylate fraction to be produced. However, as the ratio of alkylene oxide to alcohol increases, the characteristic, Conventional Broad Distribution of alkali metal catalysts can be expected. Moreover, even though the disclosed process is reported to provide a narrower distribution of ethoxylate species, the distribution is skewed so that significant amounts of the higher ethoxylates are present. For example, in Part C, over 15 percent of the ethoxylate compositions had at least three more oxyethylene groups than the average based on the reactants, and that amount in Part D is over 16 percent.
European Patent Application No. A0095562, published Dec. 12, 1983, exemplifies the ability to obtain high selectivity to low ethoxylate species when low ratios of ethylene oxide reactant to alcohol are employed as well as the tendency to rapidly loose that selectivity when higher ethoxylated products are sought. For instance, Example 1, (described as a 1 mole EO adduct), which reports the use of a diethylaluminum fluoride catalyst, employs 300 grams of a 12 to 14 carbon alcohol and 64 grams of ethylene oxide and Example 5, (described as a 1.5 mole EO adduct) using the same catalyst, employs a weight ratio of alcohol to ethylene oxide at 300:118. Based on the graphically presented data, the distributions appear to be as follows:
______________________________________ Example 1 Example 5 ______________________________________ E.sub.0 27 10 E.sub.1 50 36 E.sub.2 17 33 E.sub.3 4 16 E.sub.4 -- 6 E.sub.5 -- 2 E.sub.6 -- 1 ______________________________________
Even with a small increase in ethoxylation from the described 1 mole EO adduct to the described 1.5 mole adduct, the distribution of ethoxylate species broadened considerably with more of the higher ethoxylates being produced as can be expected from a Conventional Broad Distribution. It may be that the catalyst is consumed in the reaction process so that it is not available to provide the narrower distributions of alkoxylation product mixtures at the high adduct levels.
Several catalysts have been identified that are reported to provide molecular weight distributions for higher ethoxylates that are narrower than those expected from a Conventional Broad Distribution. In particular, this work has emphasized ethoxylation catalysis by derivatives of the Group IIA alkaline earth metals. Interest in these catalysts, which to date has been confined almost exclusively to the production of non ionic surfactants, stems from their demonstrated capability for providing hydrophobe ethoxylates having narrower molecular weight distributions, lower unreacted alcohol contents, and lower pour points than counterparts manufactured with conventional alkali metal-derived catalysts.
Recently, Yang and coworkers were granted a series of U.S. patents which describe primarily the use of unmodified or phenolic-modified oxides and hydroxides of barium and strontium as ethoxylation catalysts for producing non ionic surfactants exhibiting lower pour points, narrower molecular weight distributions, lower unreacted alcohol contents and better detergency than counterpart products prepared by state-of-the-art catalysis with alkali metal hydroxides. See U.S. Pat. Nos. 4,210,764; 4,223,164; 4,239,917; 4,254,287; 4,302,613 and 4,306,093. Significantly, these patents contain statements to the effect that the oxides and/or hydroxides of magnesium and calcium do not exhibit catalytic activity for ethoxylation, although they may function in the role of promoters for the barium and strontium compounds (U.S. Pat. No. 4,302,613).
The molecular weight distributions of the ethoxylates disclosed in these patents, while being narrower than conventional distributions, appear not to meet fully the desired narrowness. For example, FIG. 6 of U.S. Pat. No. 4,223,146 depicts the product distribution of an ethoxylate of a 12 to 14 carbon alcohol and 60 percent ethylene oxide using various catalysts. A barium hydroxide catalyst is described as providing a product mixture containing, as the most prevalent component, about 16 percent of the six mole ethoxylate. The distribution is, however, still relatively wide in that the ethoxylate species having three or more oxyethylene groups than the most prevalent component is above about 19 weight percent of the mixture and the distribution is skewed toward higher ethoxylates. The strontium hydroxide catalyst run which is also depicted on that figure appears to have a more symmetrical distribution but the most prevalent component, the seven mole ethoxylate, is present in an amount of about 14.5 weight percent and about 21 weight percent of the composition had three or more oxyethylene groups than the most prevalent component.
Also, U.S. Pat. No. 4,239,917 discloses ethoxylate distributions using barium hydroxide catalyst and a fatty alcohol. FIG. 7 of that patent illustrates the distribution at the 40 percent ethoxylation level with the four mole ethoxylate being the most prevalent component. Over about 19 weight percent of the mixture has three or more oxyethylene groups than the most prevalent component. FIG. 4 depicts the distribution of ethoxylation at the 65 percent ethoxylation level. The nine and ten mole ethoxylates are the most prevalent and each represent about 13 weight percent of the composition. The distribution is relatively symmetrical but about 17 weight percent of the composition has at least three more oxyethylene groups than the average peak (9.5 oxyethylene groups). Interestingly, comparative examples using sodium hydroxide catalyst are depicted on each of these figures and evidence the peaking that can be achieved with conventional base catalysts at low ethoxylation levels, but not at higher ethoxylation levels.
McCain and co workers have published a series of European patent applications describing the catalytic use of basic salts of alkaline earth metals especially calcium, which are soluble in the reaction medium. These applications further disclose catalyst preparation procedures involving alcohol exchange in respect to the alkoxy moiety of the metal alkoxide catalytic species. See European patent publication No. 0026544, No. 0026547, and No. 0026546, all herein incorporated by reference. These workers have also disclosed the use of strong acids to partially neutralize and thereby promote the catalytic action of certain alkaline earth metal derivatives. See U.S. Pat. Nos. 4,453,022 and 4,453,023 (barium-containing catalyst), both herein incorporated by reference. These workers also tend to confirm Yang's findings as to calcium oxide, in that McCain et al. teach that calcium oxide does not form a lower alkoxide when treated with ethanol.
In particular, calcium metal or calcium hydride is typically the starting material used by McCain et al. to make the calcium containing catalyst. These starting materials, however, are expensive. Consequently, a desire exists to use commonly found sources of calcium, such as calcium oxide (quicklime) and calcium hydroxide (slaked lime), to make calcium-containing catalysts for alkoxylation. Moreover, quicklime and slaked lime are by far the cheapest, most plentiful, least noxious, and most environmentally-acceptable of all the alkaline earth metal derivatives.
The calcium-containing catalysts disclosed by McCain et al. provide enhanced selectivities to higher alkoxylate species as compared to mixtures produced using conventional potassium hydroxide catalyst. Indeed, bases exist to believe that these calcium-containing catalysts provide narrower distributions of alkoxylates than those provided by strontium- or barium-containing catalysts. However, there is still need for improvement in providing a narrower yet distribution of alkoxylation products, particularly a distribution in which at least one component constitutes at least 20 weight percent of the composition and alkoxylation products having more than three alkoxyl groups than the average peak alkoxylation component comprise very little of the product mixture.
U.S. Pat. Nos. 4,754,075, 4,886,917 and 4,820,673, herein incorporated by reference, relates to processes for preparing alkoxylation mixtures having relatively narrow alkoxylation product distributions using modified, calcium containing catalysts. Processes are also disclosed for making alkoxylation catalysts using calcium oxide and/or calcium hydroxide as sources for the catalytically-active calcium. The alkoxylation product mixtures disclosed therein have a narrow and balanced distribution of alkoxylation species. The disclosed product mixtures are relatively free from large amounts of substantially higher alkoxylation moieties, i.e., those having at least three more alkoxyl groups than the average peak alkoxylate specie. It is stated therein that narrow distributions can be obtained where the most prevalent alkoxylation moiety has four or greater alkoxy units, that is, in the regions in which conventional catalysts provide a relatively wide range of alkoxylation species.